THE CASE OF SQUIRREL'S STOLEN NUTS

Frog is a detective who lives at the police station deep in the forest. He is wise and patient but Squirrel is the opposite right now because someone has stolen his nuts.  When Mouse is caught and admits to stealing just one nut because she was very hungry, Frog realizes there is still another nut thief still out there.  

The First Case by Ulf Nilsson is a very sweet and gentle detective story set in a wintery forest that's great for beginning chapter book readers. For readers in grades 2-4.